Water forms and changes landscapes in various ways. Oceans, seas, rivers and lakes hold and transport water across the Earth. Rivers constantly change the land by processes like runoff, sediment deposition, and the formation of landforms like meanders, flood plains, and deltas. Glaciers are also large, frozen rivers of water that can advance and shape the landscape. Watersheds delineate the areas that drain into rivers. Maps are used to represent these geographic features and changes over time.